And lest it should be supposed that Aristotle did, or professed to do, anything more than this, it ought to be remembered that he himself expressly says, at the commencement of the seventh chapter of the first book of the Meteorologics, that, with regard to things which are not manifest to the senses, he thinks to adduce sufficient reasons and demonstrations of them, if he only shows that they may be such as he explains them.43
CCV
That nevertheless there is a moral certainty that all the things of this world are such as has been here shown they may be.
But nevertheless, that I may not wrong the truth by supposing it less certain than it is, I will here distinguish two kinds of certitude. The first is called moral, that is, a certainty sufficient for the conduct of life, though, if we look to the absolute power of God, what is morally certain may be false. [Thus, those who never visited Rome do not doubt that it is a city of Italy, though it might be that all from whom they got their information were deceived]. Again, if anyone, wishing to decipher a letter written in Latin characters that are not placed in regular order, bethinks himself of reading a B wherever an A is found, and a C wherever there is a B, and thus of substituting in place of each letter the one which follows it in the order of the alphabet, and if by this means he finds that there are certain Latin words composed of these, he will not doubt that the true meaning of the writing is contained in these words, although he may discover this only by conjecture, and although it is possible that the writer of it did not arrange the letters on this principle of alphabetical order, but on some other, and thus concealed another meaning in it: for this is so improbable [especially when the cipher contains a number of words] as to seem incredible. But they who observe how many things regarding the magnet, fire, and the fabric of the whole world, are here deduced from a very small number of principles, though they deemed that I had taken them up at random and without grounds, will yet perhaps acknowledge that it could hardly happen that so many things should cohere if these principles were false.
CCVI
That we possess even more than a moral certainty of it.
Besides, there are some, even among natural, things which we judge to be absolutely certain. [Absolute certainty arises when we judge that it is impossible a thing can be otherwise than as we think it]. This certainty is founded on the metaphysical ground, that, as God is supremely good and the source of all truth, the faculty of distinguishing truth from error which he gave us, cannot be fallacious so long as we use it aright, and distinctly perceive anything by it. Of this character are the demonstrations of mathematics, the knowledge that material things exist, and the clear reasonings that are formed regarding them. The results I have given in this treatise will perhaps be admitted to a place in the class of truths that are absolutely certain, if it be considered that they are deduced in a continuous series from the first and most elementary principles of human knowledge; especially if it be sufficiently understood that we can perceive no external objects unless some local motion be caused by them in our nerves, and that such motion cannot be caused by the fixed stars, owing to their great distance from us, unless a motion be also produced in them and in the whole heavens lying between them and us: for these points being admitted, all the others, at least the more general doctrines which I have advanced regarding the world or earth [e.g., the fluidity of the heavens, Part III, Section XLVI], will appear to be almost the only possible explanations of the phenomena they present.
CCVII
That, however, I submit all my opinions to the authority of the church.
Nevertheless, lest I should presume too far, I affirm nothing, but submit all these my opinions to the authority of the church and the judgment of the more sage; and I desire no one to believe anything I may have said, unless he is constrained to admit it by the force and evidence of reason.
Appendix
Reasons Which Establish the Existence of God, and the Distinction Between the Mind and Body of Man, Disposed in Geometrical Order
(From the Reply to the Second Objections—Latin, 1670, pp. 85–91. French, Garnier, Tom. II, pp. 74–84)
Definitions
I. By the term “thought” (cogitatio, pensée), I comprehend all that is in us, so that we are immediately conscious of it. Thus, all the operations of the will, intellect, imagination, and senses, are thoughts. But I have used the word “immediately” expressly to exclude whatever follows or depends upon our thoughts: for example, voluntary motion has, in truth, thought for its source (principle), but yet it is not itself thought. [Thus walking is not a thought, but the perception or knowledge we have of our walking is.]
II. By the word “idea” I understand that form of any thought, by the immediate perception of which I am conscious of that same thought; so that I can express nothing in words, when I understand what I say, without making it certain, by this alone, that I possess the idea of the thing that is signified by these words. And thus I give the appellation idea not to the images alone that are depicted in the fantasy; on the contrary, I do not here apply this name to them, in so far as they are in
